1. Field of the Invention
The present invention pertains to a locking device for attachment to a switch or circuit breaker for locking a switch handle in a predetermined position.
2. Background
There are many applications for a locking mechanism which may be readily attached to an electrical circuit breaker or switch panel for locking one or more switches in a predetermined position of the switch handle. Some of the desiderata for such a device include the provision of a device which does not require modification of the switch panel such as by drilling or tapping for receipt of fasteners or removal of the panel face for attachment of the device.
A preferred switch locking device should also be relatively compact so as to not interfere with adjacent switches on a multi-switch panel and be relatively flat against the face of the panel to permit closure of a cabinet or enclosure box door adjacent to the panel face. Still further considerations include the provision of a device which will not substantially prevent viewing of the switch position and other identifying indicia on the face of the switch panel itself and the provision of a device which will allow a circuit breaker handle to move from an "on" position to a "tripped" position but not to a manually actuated "off" position.
Some examples of prior art switch handle locking devices which do not meet all of the desiderata indicated above, are described in U.S. Pat. Nos. 2,169,860 to F. G. Von Hoorn; 2,978,613 to E. Hein; 3,376,400 to T. N. Batt, et al; 3,595,040 to R. D. Curt; 4,006,324 to Leasher, et al; 4,260,861 to DiMarco; 4,300,030 to DiMarco, et al; and 4,467,152 to Gordy. The handle locking devices disclosed in the above identified patents require special modification of the switch panel or enclosure, are characterized by relatively complex structures which are designed in such a way that they must be retained on the switch panel itself and are not self-retaining as a result of engagement with a switch handle, or are relatively bulky and require more space than is commonly provided in many electrical switch installations. However, the present invention overcomes several disadvantages of prior art devices as will be appreciated by those skilled in the art upon reading the following summary and detailed description.